1. Field of the Invention
The present invention generally relates to a method for manufacturing a wooden golf head and, more particularly, to a method for manufacturing a high-strength steel golf head with a thin striking faceplate.
2. Description of the Related Art
Early wooden golf heads are made of stainless or carbon steel. In order to increase the performance of the wooden golf heads, several new steel-type casting materials have been continuously developed in recent years and have been used to manufacture wooden golf heads. For example, steel-type alloys containing cobalt (Co), molybdenum (Mo), or titanium (Ti) generally have a high strength above 240 ksi. Therefore, such steel-type alloys are suitable for manufacturing the wooden golf heads, thinning the striking faceplate of the wooden golf heads, decreasing the total weight of the wooden golf heads and improving the hitting effect of the wooden golf heads.
Current wooden golf heads are manufactured by using a high frequency induction furnace to rapidly melt the casting materials in the atmosphere, followed by removing the slag and gases in the molten metal by slagging and refinery. Static gravity pouring is then carried out. However, the casting materials for the high-strength wooden golf heads include active metals, such as cobalt, molybdenum, or titanium that are apt to react with oxygen in the air. Thus, rigorous oxidation easily occurs during the procedures of smelting of the casting materials, increasing difficulties in melting and easily causing oxidative fire cracks due to reaction with air during the pouring process. As a result, appearance defects, such as sesame dot defects and black bean defects, are apt to be formed on the cast products of the wooden golf heads. In worse situations, the reactive gas forms a large number of slag holes or blowholes in the cast products of the wooden golf heads and, thus, adversely affects the tensile strength of the wooden golf heads.
Namely, to assure that the striking faceplate of a wooden golf head can meet the tensile strength standard for withstanding cannon shots of predetermined strength and times without damage, the thickness of the striking faceplate of a current integrally formed wooden golf head is still too thick. TABLE 1 shows the tensile strengths and minimum thicknesses of striking faceplates of wooden, golf heads made of different materials by gravity pouring in the atmosphere, wherein the “minimum thickness” is defined as the minimum thickness of a striking faceplate having a strength capable of withstanding 3,000 cannon shots at a speed of 50 m/s without damage (not including the groove depth).
TABLE 1striking faceplatetensile strengthminimum thicknessmaterial(ksi)(mm)NANO 5583.20303773.20304773.208620 853.20MS225982.85M-9982.90low hardness 4311002.85ST-231023.204311102.85LD-7451202.82205 1252.7017-4PH1402.7ST-221492.754501702.454501802.35HYPER17-412002.3AM3552102.3ES2302302.204130 2302.154130 2302.15ES2352352.20SUP 102362.2015-7 PH2402.204552502.10465 + (275)2702.054752802.00
As can be seen from Table 1, to achieve the same cannon shot conditions, the tensile strength and the minimum thickness of each striking faceplate material are highly related. Namely, the minimum thickness can be smaller if the tensile strength of the striking faceplate is higher. Furthermore, given the above cannon shot conditions, the average minimum thickness (not including the groove depth) of the striking faceplate of a current integrally formed wooden golf head is about 2.59 mm. For a striking faceplate having a higher strength (above 240 ksi), the minimum thickness (not including the groove depth) has to be more than 2.0 mm. Thus, there is a bottleneck in reducing the overall weight of current wooden golf heads.
Furthermore, rigorous oxidation also reduces the flowability of the molten metal in the shell mold, leading to a reduced yield rate of the cast products of the wooden golf heads due to insufficient pouring or resulting in gaps in the cast products of the wooden golf heads due to cold shut. The tensile strength of the cast products of the wooden golf heads is also adversely affected.
On the other hand, on the wooden golf heads manufactured by static gravity pouring, additional casting materials are needed to elevate the pressing effect of the molten metal and to improve the yield rate of the wooden golf heads. However, the additional casting materials and the energy used for melting the additional casting materials result in the increased manufacturing cost.
In light of this, it is necessary to improve the conventional method for manufacturing a steel golf head.